The present invention relates to guide apparatus, probes, and the like, and particularly to guide apparatus that are steerable through body cavities and aimable at obstructions, organs, or tissue within the body from a position external to the body. More particularly, the present invention relates to maneuverable guide apparatus including spring means for biasing a temperature-activated memory element to alter the shape of the memory element upon cooling of the memory element to a temperature below its martensitic transformation temperature.
Some attempts have been made in the past to provide catheters having distal ends which, when inserted into a body, are manipulatable to advance the catheter through body cavities. See for example, U.S. Pat. Nos. 3,674,014 and 3,773,034. The catheter disclosed in U.S. Pat. No. 3,674,014 includes permanent magnets and employs a magnetic field to bend the distal end of the catheter. The catheter disclosed in U.S. Pat. No. 3,773,034 includes fluid conduits and employs a fluid to bend the distal end of the catheter. Other controlled devices are disclosed in U.S. Pat. Nos. 3,605,725 and 4,176,662. However, these prior devices are quite difficult to control and manipulate.
Some work has previously been done to produce a catheter which is readily insertable while being effectively anchorable in a body cavity. See, for example, U.S. Pat. Nos. 3,729,008 and 3,890,977.
In U.S. Pat. No. 3,890,977 to Wilson, the distal end of the catheter is formed into a desired shape by using a material exhibiting mechanical memory that is triggered by heat. By heating the mechanical memory material, the distal end of the catheter is shaped to anchor the catheter within the body. However, the change of the shape or other movement of the distal end in these prior devices is limited to a single direction. Once the memory material has been heated causing the distal end to move in said single direction to assume its characteristic anchoring shape, it becomes necessary to deform the distal end manually at a temperature below the transition temperature of the mechanical memory material in order to change the shape of the distal end. The need for manual manipulation of a catheter once it is inserted into body limits the steerability and aimability of the catheter.
Other devices are known for guiding a catheter to a particular location within the body. See for example U.S. Pat. No. 3,043,309.
One object of the present invention is to provide a steerable guide apparatus, probe, and the like which is easy to operate and steerable in a plurality of different directions within the body.
Another object of the present invention is to provide an aimable guide apparatus, probe, and the like which is easy to operate and which can be aimed at obstructions, organs, or tissues in a plurality of different directions within the body.
Yet another object of the present invention is to provide a guide apparatus, probe, and the like of improved maneuverability having means for slidably coupling each of a plurality of temperature-activated memory elements to a core member so that each memory element is permitted to slip in relation to the adjacent core member when at least one of the memory elements is heated to assume a predetermined "memorized" shape.
Another object of the present invention is to provide a steerable and aimable guide apparatus, probe, and the like of very simple design having only one temperature-activated memory element that is movable to a predetermined shape using remote controls to steer and aim the guide apparatus and yet is automatically returnable to an initial shape without manual manipulation by an operator.
Still another object of the present invention is to provide a highly maneuverable guide apparatus, probe, and the like having at least one resilient element for biasing the distal end of the guide apparatus to assume an initial shape and a separate temperature-activated memory element that is movable under heat to bend the distal end of the guide apparatus to a multiplicity of shapes other than the initial shape.
Another object of the present invention is to provide a steerable and aimable guide apparatus, probe, and the like of simple construction wherein a memory element is employed to deflect a guide wire made of spring material.
Yet another object of the present invention is to provide a steerable and aimable guide apparatus, probe, and the like wherein the guide wire is made of a resilient shape-memory material.
Still another object of the present invention is to provide a steerable and aimable guide apparatus, probe, and the like wherein a temperature-activated memory element made of a shape-memory alloy and employed to deflect a guide wire made of spring material is coupled to the guide wire to apply an axial compression pulling force to the guide wire as the length of the memory element is shortened upon being heated to a predetermined temperature in accordance with a thermal property of the shape-memory alloy so that the guide wire is "pulled" along its axis by the memory element to assume a different shape.
According to the present invention, a maneuverable distal apparatus includes a temperature-activated memory element moving in a first direction to assume a predetermined shape when heated to a predetermined temperature and spring means for yieldably urging the memory element in a second direction away from the first direction upon cooling of the memory element to a temperature less than the predetermined temperature so that the memory element is moved to assume a shape other than the predetermined shape. The apparatus also includes insulation means for preventing unwanted electrically conductive contact between the memory element and the spring means and control means for selectively heating the memory element so that the memory element is moved in the first direction.
In preferred embodiments, the spring means is an elongated coil spring formed to include a longitudinal cavity and the memory element is positioned in the longitudinal cavity. The insulation means includes a tubular sleeve positioned in the longitudinal cavity and the memory element is positioned in the tubular sleeve. An end cap is coupled to a distal end of the elongated coil spring and the insulation means includes means for preventing electrically conductive contact between the memory element and the end cap.
The control means includes power supply means, first electrical lead means for coupling the power supply means and the spring means in electrical communication, and second electrical lead means for coupling the power supply means and the memory element in electrical communication. Circuit means interconnecting the spring means and the memory element is provided for establishing an electrical circuit electrically connecting the spring means, the memory element, and the control means in series.
In another preferred embodiment, the guide wire is a tubular coiled spring made of a resilient shape-memory alloy. Control means is provided for selectively heating the tubular coiled spring to at least a predetermined temperature so that the tubular coiled spring moves from its initial shape to assume its predetermined shape. The tubular coiled spring returns toward its initial shape upon being cooled to a temperature less than the predetermined temperature.
In yet another embodiment, the memory element is disposed inside a hollow axially compressible guide wire made of spring material and anchored at its opposite ends to spaced-apart distal and proximal portions of the guide wire. The "double-anchored" memory element shortens in length in accordance with due to a characteristic thermal property of the shape-memory alloy comprising the memory element upon being heated to a predetermined temperature. Such shortening acts to apply an axial compression load to the axially compressible guide wire, thereby effectively "pulling" the guide wire to assume a different shape. The guide wire returns toward its initial shape upon cooling of the memory element to a temperature less than the predetermined temperature due, in part, to spring characteristics of the guide wire. One notable advantage of this double-anchored feature is that the size and mass of the memory element can be reduced significantly in comparison to other embodiments since less force is required to pull the guide wire to a different shape than to push the guide wire to the same shape. It will be understood that "pulling" refers generally to axial compression loading or the like of the guide wire, while "pushing" refers generally to transverse shear loading or the like of the guide wire.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of preferred embodiments exemplifying the best mode of carrying out the invention as presently perceived.